1. Technical Field
The present invention relates generally to manufacturing semiconductor wafers and more particularly the invention pertains to the field of Chemical Mechanical Polish (CMP) used during the fabrication of semiconductor chips to planarize the wafers.
2. Background Art
Rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections which connect active areas. As a result, the tolerances regarding the planeness or flatness of the semiconductor wafers used in these processes are becoming smaller and smaller. One customary way of flattening the surfaces of semiconductor wafers is to polish them with a polishing apparatus.
Such a polishing apparatus has a rotating wafer carrier assembly in contact with a polishing pad. The polishing pad is mounted on a rotating turntable which is driven by an external driving force. The polishing apparatus causes a polishing or rubbing movement between the surface of each thin semiconductor wafer and the polishing pad while dispersing a polishing slurry to obtain a chemical mechanical polish (CMP). CMP in planarization requires the wafer surface to be brought into contact with a rotating pad saturated with either a slurry of abrasive particles or a reactive solution, or both, that attacks the wafer surface. This is done while exerting force between the wafer and polishing pad. The abrasive particles can scratch the surface during the polish operation especially if they agglomerate or if abrasive material becomes embedded in the polishing pad. Also, after polishing is completed and the wafer is rinsed to remove the abrasive particles, some of the abrasive particles will remain on the wafer surface or pad by simply being imbedded into the surface or strongly attracted to the surface.
The scratches can cause problems in subsequent processing steps as for example in a Damascene process, intra-level where shorting could result. Leaving the particles on the wafer or pad can likewise lead to process problems, most notably photolithographic and etching defects in subsequently processed levels.
Prior art for particle removal involves either a mechanical clean, such as a brush clean, after the wafers have been removed from the polishing apparatus and dried, or a washing step with a surfactant (soap) performed prior to the wafer being dried as disclosed in U.S. Pat. No. 5,320,706, issued to Blackwell on Jun. 14, 1994 and assigned to Texas Instruments Incorporated. These processes are not usually 100% effective and do not address the scratching problem. Therefore, it appears that no prior art per se exists that addresses the scratching problem directly.
The present invention discloses a method and apparatus for removing slurry abrasive particles in a polishing process for planarization of a semiconductor wafer.
The present invention discloses a method and apparatus for reducing the size of the slurry abrasive particles or agglomerations of slurry abrasive particles in a polishing process for planarization of a semiconductor wafer.
The present invention disclose a method for reduction in size of agglomerations and removal of abrasive particles from the polishing pad during a polishing process for planarization of a wafer, comprising: applying a high pressure mixture of gas and liquids to the polishing pad to reduce and remove the agglomeration of abrasive particles.
The present invention is a method for removal of abrasive particles and conditioning the polishing pad during a polishing process for planarization of a wafer, comprising: applying a high pressure mixture of gas and liquid to the polishing pad to remove the abrasive particles and condition the pad.
The present invention discloses an apparatus comprising: a wafer; a polishing pad which planarizes the wafer; a slurry dispenser which provides slurry containing abrasive particles to the polishing pad; and a high pressure fluid dispenser which controllably provides a mixture of gas and fluid to the polishing pad.
In accordance with the above, it is an advantage of the present invention to solve the problem of slurry abrasive particle removal post-CMP and the problem of scratches on the post-CMP surface.
It is an advantage of the present invention to remove the abrasive particles from the pad.
It is an advantage of the present invention to rapidly remove and reduce the abrasive particle size while conditioning the pad.
It is an advantage of the present invention to rapidly reduce the size of agglomerations of abrasive particles.
It is an advantage of the present invention to eliminate residual slurry and slurry abrasives and particulates from the polishing pad. It is an advantage of the present invention to break up or reduce the size of abrasive particle agglomerations.
It is an advantage of the present invention to eliminate slurry abrasive particle residues and reduce if not eliminate the sources of scratches.